Question

If a circle with the centre (2, 3) passes through the point (-1, -1), find the radius of the circle.

• A. 5

Answer 1

The correct option is A 5
Given: Centre (2, 3) and point (-1, -1)

The distance between two points $(x_1,y_1)\text{and}(x_2,y_2)$ is $\sqrt{(x_2-x_1{)}^2+(y_2-y_1{)}^2}.$

So, radius = $\sqrt{(-1-2{)}^2+(-1-3{)}^2}$

Radius = $\sqrt{(-3{)}^2+(-4{)}^2}$

Radius = $\sqrt{9+16}$

Radius = $\sqrt{25}$

Radius = 5 units